#include <fstream>

using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");
int dp[1025][1025];
int A[1025],B[1025];
void drum(int i,int j)
{
    if(i==0||j==0) return;
    if(A[i]==B[j])
    {
        drum(i-1,j-1);
        fout<<A[i]<<" ";
    }
    else
    {
        if(dp[i][j]==dp[i-1][j]) drum(i-1,j);
        else drum(i,j-1);
    }
}
int main()
{
    int n,m,i,j;
    fin>>n>>m;
    for(i=1;i<=n;i++) fin>>A[i];
    for(i=1;i<=m;i++) fin>>B[i];
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        {
            if(A[i]==B[j]) dp[i][j]=dp[i-1][j-1]+1;
            else dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
        }
    }
    fout<<dp[n][m]<<"\n";
    drum(n,m);
}